Hey everyone I recently upgraded to 275/70/18 Falken AT3W. Tires are great so far. I also have the SCT4 with omega tune. With the factory tune my speedometer is 1 MPH slower than garmin gps shows. I went to falken website and they say the tire specs out at 33.4”. So I upload my omega tune with this size and speedo reads 1mph faster than the garmin gps? So I measure the tire height and get 32.8 with them on the truck. Plug that data in and speedo still 1mph faster than gps. So now I go from 32.8” to 33.4” in .2” increments, and speedo still 1mph faster than than gps. Except going up or down hills the speeds match, but on flat ground speedo is 1mph faster? Am I doing something wrong ? Or is this pretty common? First time I’ve ever used a tuner to update speedometer after tire upgrade. Any help would be greatly appreciated! And thanks in advance.
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